Astronomers at four Irish third level institutions have participated in the detection of pulsed gamma-ray emission from the Crab Pulsar at energies far beyond what current theoretical models of pulsars can explain.

With energies exceeding 100 billion electron volts the surprising gamma-ray pulses were detected by the international VERITAS collaboration using an array of telescopes at the Whipple Observatory in Arizona. Their results are published in a paper in the October 7th issue of the prestigious journal Science

The Irish scientists have been involved in the search for this pulsed emission for over two decades. The Irish team members include Dr John Quinn at University College Dublin, Dr Gary Gillanders and Dr Mark Lang at the NUI Galway, Dr Paul Reynolds at Cork Institute of Technology and Dr Pat Moriarty at Galway-Mayo Institute of Technology.

The Crab pulsar is a rapidly spinning neutron star, the collapsed core of a massive star that exploded in a spectacular supernova in the year 1054, leaving behind the brilliant Crab Nebula with the pulsar at its heart. Spinning at 30 times a second the pulsar emits a rotating beam of radiation like a lighthouse beacon. Current theoretical models of the pulsar predict that the maximum energy of pulsed gamma-rays should be about 10 billion electron volts so it was very significant to find emission with energies ten times higher. Further observations to characterise the very high energy gamma-ray emission and new theoretical models will be required to explain the physical mechanism behind it.

The Irish involvement in VERITAS is part funded by Science Foundation Ireland.